The purpose of this investigation is to elucidate the biochemical and physiological mechanisms involved in the development of mature cataracts. Although the immediate concern is for the type of cataract classified as carbohydrate cataracts, it is felt that the determination of the chain of events involved in the formation of this type of cataract may well involve changes which also occur in the formation of other types of cataracts. Mature galactose cataracts can be produced in tissue culture. This development provides a mechanism for studying cataract development in a controlled environment. Studies will be made to correlate the changes in chemical composition and biochemical activity with the time required for the development of cataracts in rat lenses under various conditions. Variations in the composition of the media, the introduction of metabolic inhibitors, and the addition of hormones will be used to stimulate cataractogenic conditions and establish correlations. Other cataractogenic agents will also be studied to determine similarities and differences in the chain of events that are involved in the production of lens cataracts. Lens swelling has been implicated as a major factor in cataractogenesis. This can be simulated in an hypotonic medium. However, swelling is countered by a process known as "volume regulation". Therefore, this process will be studied to determine its relationship to cataract formation.